Earthquakes are occurring more frequently in parts of the U.S. where they have historically been rare, and quake hazard is rising for people not used to thinking about or preparing for it.

Central U.S. Earthquake ConsortiumThe rising risk was underlined Wednesday by the release by the U.S. Geological Survey of an update to the U.S. National Seismic Hazard Maps, noting hazard in the central U.S. and on the East Coast higher than previously thought. Among the highest risk states: Missouri and Illinois.

According to the USGS, the frequency of earthquakes in the central and eastern U.S. has quintupled, to an average of 100 a year during the 2011-2013 period, up from only 20 per year during the 30-year period to 2000.

Most of these quakes were minor, but research published by the USGS earlier this year demonstrated that a relatively minor magnitude 5.0 quake caused by wastewater injection after conventional oil drilling triggered a much bigger, 5.7 magnitude quake in Prague, Okla.

“We know the hazard has increased for small and moderate size earthquakes. We don’t know as well how much the hazard has increased for large earthquakes. Our suspicion is it has but we are working on understanding this,” said William Ellsworth, a scientist with the USGS.

Insurers are alarmed about higher quake risk. “I worry that we will wake up one morning and see earthquake damage in our country that is as bad as that has occurred in some developing nations that have experienced large earthquakes,” said Carl Hedde, head of risk accumulation at Munich Re America. “Beyond building collapse, a large amount of our infrastructure could be immediately damaged. Our roads, bridges and energy transmission systems can be severely impacted.”

Walmart Stores Inc., with its huge network of stores and facilities, has also taken note. ”We are seeing increased earthquake activity in the central U.S. That is an area we are focusing on even more,” said Mark Cooper, senior director of emergency management at Walmart, in an interview. He explained that Walmart takes an “all-hazard” approach to emergency preparedness, but focuses on specific risks in areas of the country where those risks are particularly relevant, such as hurricanes in Louisiana. “A few weeks ago, we participated in an exercise to prepare for an earthquake on the New Madrid fault line,” he said.

The New Madrid seismic zone was the site of massive earthquakes in 1811-1812 that rerouted the Mississippi River. Mark Petersen, project chief for the National Seismic Hazard Project of the U.S. Geological Survey, told Risk & Compliance Journal that a recent report concluded that recent seismic activity there is signaling a new hazard. “Earthquakes are quite rare in many places but when they happen they cause very intense damage because people have not prepared,” he said.

Yet officials say it’s difficult to convince businesses and residents to take the risk seriously in places such as Ohio, where minor earthquakes have occurred in connection with re-injection of wastewater into the ground after fracking. ”We aren’t California, where it’s part of their everyday living, the way snowstorms are part of our everyday living,” said Tamara McBride, spokesperson for the Ohio Emergency Management Agency.

Brian Blake, program manager for the Central U.S. Earthquake Consortium, a non-profit organization of public and private sector entities, noted that there is a 25% chance of a magnitude 6 or greater quake in the New Madrid zone in a 50-year period, and the last one occurred in 1895. “That size earthquake happens every 100 years or so,” he said.

But 100 years gives people plenty of time to forget. “Obviously the building codes throughout the central U.S. do not generally take earthquake risk or the risk of a large earthquake into account,” said Elizabeth Cochran, a seismologist with the USGS.